Volume 9, Issue 2 (March 1981)
Quenching, Tempering, and Aging Chromium-Molybdenum-Vanadium Cast Steels
The usual specifications for Cr-Mo-V steel castings fix modest levels of yield strength (350 to 450 MPa) in the hope of obtaining acceptable toughness. But this optimism sometimes leads to disappointment when only the components themselves are considered and not the attached parts. Tests carried out on Cr-Mo steel casings that have 100 000 h or more of service life show that, if toughness is sufficiently high in the as-received condition, and if certain precautions are taken into account at start-up, one may accept service embrittlement and even allow casings that reveal cracks caused by creep or thermal fatigue to remain in service. The aim of the work discussed in this paper has been to compare different grades of Cr-Mo steel distinguished in particular by chromium and nickel contents. Two subjects have been dealt with: the influence of the chemical composition on the optimal conditions of hardening and tempering and the preliminary study of age embrittlement (evaluated by the translation of Charpy V-notch and ductile fracture toughness transition curves).